FIG. 11 is a circuit diagram showing a constitution example of a front electronic equipment system in a related art. A front ECU (Electronic Control Unit) 100 is connected with a power source line for supplying a power source from a battery, a main multiplexed line connected with a LAN (Local Area Network) for vehicle communicated by a protocol of CAN (Controller Area Network) or the like, various front auxiliary equipments, rear auxiliary equipments, sensors and switches.
The front ECU 100 is connected with head lamps 154RH, 154LH, side marker lamps 184RH, 184LH, clearance lamps 174aRH, 174aLH, front fog lamps 164RH, 164LH, cornering lamps 174bRH, 174bLH, horns 104aHI, 104bLO, and a front washer motor 194b as front auxiliary equipments by wire harnesses. Further, the front ECU100 is connected with a rear washer motor 254 as a rear auxiliary equipment. Further, the front ECU100 is connected with a horn switch 104e, a hood curtsy switch 104f, a washer level sensor 194a and a head lamp cleaner relay 104c by wire harnesses.
The front ECU100 is mounted with a CPU input interface for inputting signals inputted from switches and sensors to the CPU, an output interface for outputting signals to the head lamp cleaner relay 104c, and devices (semiconductor switches and mechanical relays) for driving lamps, motors and horns mounted to various auxiliary equipments, not illustrated at inside thereof.
As a related art of the invention, JP-A-2001-287605 discloses an optional LAN connecting wire harnesses capable of achieving common formation of main control apparatus constituting a basis even when modes of vehicles differ and capable of reducing cost. In this publication, a electronic equipment in a vehicle is controlled from sub ECU through gate wire harnesses.
According to the front electronic equipment system of the related art shown in FIG. 11, drive signals to various auxiliary equipments are transmitted from the front ECU to the auxiliary equipments respectively via wire harnesses. Signals from various sensors and switches are also inputted respectively by wire harnesses and therefore, a number of connector poles of the front ECU is increased and a number of pieces of the wire harnesses is also increased.
Therefore, when specifications/functions of front auxiliary equipments are changed, the wire harnesses connected to the front ECU need to change and kinds and numbers of the wire harnesses are also increased. Particularly, when functions of the front auxiliary equipments are increased, a number of circuits is increased and the wire harnesses become bulky to bring about an increase in mass thereof. At the same time, the front ECU also becomes bulky to bring about an increase in mass (deterioration of fuel/running function) and a deterioration in mountability and also softwares mounted to the front ECU become bulky. Thereby, a number of articles of the front ECUs is increased to thereby increase in a number of steps of development, addition to specifications/increase in numbers of steps of changing.
Further, the front ECU is mounted with a number of load drive devices (semiconductor switches or mechanical relays) and therefore, small-sized formation thereof is difficult and a problem of heat generation is also caused.
Further, when lamps, motors and the like in the auxiliary equipments are driven by PWM (Pulse Width Modulation) control, there also poses a problem of emitting noise from the wire harnesses to the lamps or motors. For example, an adverse influence is effected on an antenna cable of a radio or the like thereby.
In this respect, according to JP-A-2001-287605, the problems are improved by providing sub ECU. The invention discloses the technology of drastically resolving the problems by further developing JP-A-2001-287605.